TextBooks Science Form 1 (DLP)

190 Chapter 6 Compound combine
chemically

Method of Changes in arranged in
separation substance Metal
Electrolysis
Physical Chemical Element Periodic Table
change change consists classified
of into

Atom Non-metal Semi-metal

Mixture combine Subatomic
physically particles
can be differentiated
Separation Proton through
method Electron Appearance
Neutron Ductility
Filtration Malleability
Electrical and
Distillation heat conductivity
Boiling point and
Separation by melting point
using magnet

Sedimentation

Floatation

Chromatography

PJCaehdnaugpaetlneBrale6ar:nkPakeleraipoaddiac PTeanbyleiasatan Saintifik

After studying this chapter, you can:
6.1 Classification of Elements

Conclude that all matter consists of atoms.
Differentiate between atoms and molecules as well as elements and compounds.
Identify the position of metals, non-metals and inert gases in the Periodic Table.
Differentiate the characteristics of metals and non-metals.
6.2 Mixtures
Communicate about examples of mixtures in daily life.
Solve problems of separating mixtures.
6.3 Compounds
Communicate about compounds in daily life.
Demonstrate the formation of compounds from metals and non-metals.
Conclude that mass is conserved during chemical change.
Separate compounds through chemical methods.
Differentiate between chemical change and physical change.
Differentiate between mixtures and compounds.

Summative Practice 6

1. Figure 1 shows three shapes - circle, square and pentagon which represent atoms from
different elements.
Based on Figure 1, identify the combination of atoms that represent
(a) molecule of a compound.
(b) molecule of an element that consists of two atoms.
(c) molecule of an element that consists of three atoms.

(a) (b) (d)
(c)
(e)
(f) (g) (h)

(i) (j) (m)
(l)
(k)
(n) (p)

(o)
Figure 1

ChapBtaebr 6 191

2. Figure 2 shows part of the Periodic Table.

P
R

Figure 2
(a) State the type of element for P and R.
(b) What are the differences in physical characteristics of P and R?
(c) Iron is a type of metal that has a shiny surface. However, iron can rust easily.
Explain.
(d) Graphite is an example of carbon. What are the characteristics of graphite that make it

suitable to be used as pencil lead?
3. Noraini wants to make pineapple jam using the recipe given by her mother as shown
in Figure 3.

Pineapple Jam
1. Remove pineapple skin and grate the pineapple.
2. Blend the pineapple using a blender.
3. Remove the excess juice.
4. Cook the blended pineapple on medium heat. Add some sugar, salt

and yellow food colouring.
5. Stir the mixture until it thickens and is sticky.
6. Then, cool the jam and keep it in the refrigerator.

Figure 3
(a) Name the separation method used in the recipe.
(b) Which step involves the separation method that you stated in 3(a)?

4. Kumutha is given a mixture of sand, iron filings, sawdust and salt. She separates the mixture
by following the four steps in Figure 4. The letters A, B, C and D represent the substances in
the mixture.

192 Chapter 6

CPJaehdnaugpaetlneBrale6ar:nkPakeleraipoaddiac PTeanbyleiasatan Saintifik

A, B, C, D

Step 1: B, C, D A
Magnetic attraction

B, C, D

Step 2: C + D + water B
Dissolve in water and
remove substance
that float

C + D + water

Step 3: D + water C
Filtration

D + water

Step 4: water D
Evaporation of

water

Figure 4

(a) Identify substance A, B, C and D whether they are sand, iron filings, sawdust or salt.
(b) Differentiate the density of B and C. Why can B be separated from the mixture in Step 2?

Explain.
(c) If D is replaced with sugar, can it still be separated from the water by applying

Step 4?
(d) Is there another way that Kumutha could do to separate the mixture in Step 4? Explain

your answer.

5. A few students set up the apparatus as shown Glass rod Beaker
in Figure 5 to separate sand and salt. They Mixture of sand
found out that the mixture took a longer time Retort stand and salt solution
to be filtered. Therefore, they decided to stir the with clamp Filter funnel
mixture on the filter paper using a glass rod. Is Filter paper Sand
it a good idea? Give your reason (s).
Salt solution

Figure 5
6. Athirah accidentaly spills sand into a salt container. How can she separate the salt and sand

from the mixture? State the separation method that she needs to use. Explain the steps in the
separation method.

ChapBtaebr 6 193

7 AirChapter

Why must we take care of the air
around us?

What is the composition of the air?
How can we maintain the quality

of the air?

Let’s Study:

Composition of Air
Combustion
Air Pollution

194 BCChahabapp7tteerr76

PUCehdnagpreatneral7a:nAkierpada Penyiasatan Saintifik

F SCIENCE BULLETINA ihchnwaIiIatoPenndhizERuaodtveeoMahnlaleitrcllsstchxuroPractetaeitchloodA(euasaOaAerfspnsystdl.eoittPlisLahrhaPadiIIanmaesenr)htLbtcaoodapoaaeylslrenttUevnoeyhtxodoteinvoht?pTppageoabeteurlrerheAieoanftdreet,ehlbhrnbwNeohldaeeeusradeesmpiAroTzcpvxtneyetaeispihic.crd.cneaIieeWetPPagrfNrifislgvoeeelch,ioyielnDncoa vlputcuattenslhiEtrnniee naetostahngXaarbsAreitsreybeeisyr(AP ktcIonl)waTosawaIs05Tb1ri2N-df1t0lhA05ihes-c1i101ePsaMo1--0t2I3liuie0nA0o0rAvd0in0hreeeLloxPafooilAfLAstlhlaeYuiu.riVvstrTaPeeSeqaUdlMnrobIuytolnGalAalofIeUushlndoiPte1atndeaoyaorhnedgslalxteathluhtuanIoei(ynlddtAwtidehoPiseytnfIsxto)h.irlmeeuvpseatlcot
Hazardous
>300

Oxygen Xenon
Carbon dioxide Carbon cycle
Nitrogen Oxygen cycle
Inert gases Global warming
Helium Greenhouse effect
Neon Combustion
Argon Fire extinguisher
Krypton Air pollution

CChhaapptteerr77 195

7.1 Composition of Air

Let’s learn

• Plan ways to determine and record the composition of air.
• Synthesise the composition of air from a pie chart.
• Justify the importance of oxygen, nitrogen, carbon dioxide and inert gases in daily life.
• Appreciate the carbon cycle and the oxygen cycle in maintaining the composition of gases in the air.
• Solve problems when there is/are interferences to the oxygen and the carbon cycle.

Y ou have learned that air has mass and occupies space in

Chapter 5. All living things need air to survive. Clean
air does not have colour or smell. Therefore, we cannot
see the air even though it has a lot of substances in it.
(Photograph 7.1).

What are the contents of air? Air is a mixture
of several gases which are nitrogen (78%), oxygen
(21%), carbon dioxide (0.03%) and inert gases
(0.97%) such as helium, argon, neon, xenon and
krypton.

Other components that exist in the air are Photograph 7.1 Air cannot be seen
microorganisms, water vapour and dust. The quantity of
these components is low and varies according to place and
time. For example, there is more water vapour in forests or
after the rain than during a hot day.

Nitrogen B
78%
What is the relationship
Carbon between the water vapour
dioxide content in the air and
0.03% formation of cloud and rain?

Science Exploration

Some sicknesses such
as fever are caused by
Inert gases microorganisms in the air.
and other

substances

Oxygen 0.97%

21%

Figure 7.1 Composition of air represented in a pie chart

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Carry out Activity 7.1 to determine the percentage of oxygen in the air.

7.1

Aim: To determine the percentage of oxygen in the air
Materials and apparatus: Candle, plasticine, matches, glass basin, permanent marker pen,
gas jar, gas jar stand, water.
Instruction

The gas jar is

Gas jar Candle Gas divided into
jar five equal parts
Water level Glass and marked
indicator basin with marker
pen
Gas jar
stand Water Water

Plasticine level

(a) indicator (b)

Figure 7.2 Set-up of apparatus before the candle is lit

1. Prepare the apparatus as shown in Figure 7.2 (a).
2. Divide the gas jar into five equal parts
(Figure 7.2 (b)).
3. Light the candle and invert the gas jar over the Candle

candle (Figure 7.3).
4. Observe and record the changes in the water level
when the flame extinguishes.
5. Make a conclusion on the percentage of oxygen
in the air. Figure 7.3 Set-up of apparatus after

Questions the candle is lit

1. What happened to the flame of the candle after a period of time? Why?
2. What happened to the water level at the end of this activity? Give reason(s) to the
changes.
3. What is the percentage of oxygen in the air based on this activity?



At the end of Activity 7.1, the water rose to one fifth of the gas jar. This shows that one
fifth of the air contains oxygen. Therefore, the air consists of 20% oxygen.

Chapter 7 197

Is Air a Mixture? Air is a mixture.

Is air a
compound or a

mixture?

Figure 7.4 Air is a mixture

Do you still remember the differences between mixtures and compounds which you have
learned in Chapter 6? Why is air classified as a mixture and not a compound?

Air is a mixture because the components can be separated by a physical method,
which is fractional distillation.

Science Exploration

The Importance of Gases Fractional distillation is
separation of a liquid
Have you ever imagined life without air? What is the mixture into fractions
importance of oxygen, carbon dioxide, nitrogen and with different boiling
inert gases? points through boiling
and condensation.

Photograph 7.2 One of the importance of oxygen is
for combustion

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PCUehdnagpreatneral7a:nAkierpada Penyiasatan Saintifik

Importance of
gases

Oxygen Carbon dioxide Nitrogen Inert gas

Rocket Fire Nitrogen fertiliser Light bulb
extinguisher
• Respiration • Production of • Helium is used
• Combustion of • Photosynthesis nitric acid and to fill hot air
• Production ammonia balloons and
rocket engine at weather balloons
high altitudes of carbonated • Nitrogen cycle
• Welding and drinks • Liquid nitrogen • Neon gas is used
steel cutting • Fire extinguisher in advertising
• Preparation • Carbon cycle as cooling agent lights
of various
compounds • Argon gas is used
in light bulbs

Oxygen

Helium

Carbon
dioxide

Figure 7.5 Importance of gases

Chapter 7 199

Carbon cycle

Carbon dioxide in atmosphere

decomposition burning of
respiration fossil fuels

photosynthesis

respiration

is eaten

Animal

Green plants

dead organisms

Release carbon dioxide form fossil fuels
Use carbon dioxide (petroleum, natural gas and coal)

Figure 7.6 The carbon cycle

How does the carbon cycle maintain the content of carbon dioxide in the air?

Carbon cycle is the cycle • Carbon cycle begins when green plants absorb
that maintains the content of carbon dioxide through photosynthesis.
carbon dioxide in the air by
continuously taking carbon • Animals that eat the plants obtain carbon elements
dioxide from the air and from them.
returning it to the air.
• When the plants and animals die, they decompose.
• Decomposition caused by bacteria and fungi in the

soil releases carbon dioxide.
• Burning of fossil fuels that contain carbon like coal

and petrol also releases carbon dioxide.
• During respiration, all plants and animals release

carbon dioxide.
• These processes such as decomposition, combustion

and respiration are balanced by photosynthesis.

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Oxygen Cycle

Photosynthesis Oxygen in atmosphere Respiration
Respiration Combustion

Green plants Rusting Animals
Decomposition
Decomposition Carbon dioxide in atmosphere
of waste Figure 7.7 The oxygen cycle of waste
materials and
materials and dead organisms
dead organisms
Video on oxygen
Use oxygen cycle
Release oxygen

How does the oxygen cycle maintain the content of oxygen in the air?

Oxygen cycle is a continuous cycle that • Oxygen needed in respiration, rusting,
takes oxygen from the air and returns it combustion and decomposition is
to the air. obtained from photosynthesis.

We must always appreciate the carbon and oxygen cycles that maintain the gas content in the air.
All activities that harm the air must be reduced.

Chapter 7 201

7.2

Aim: To gather information regarding the importance of gases, the oxygen cycle and
carbon cycle
Instruction
1. Work in groups.
2. Find information on the importance of the following gases:
(a) oxygen
(b) carbon dioxide
(c) nitrogen
(d) inert gases
3. Record the information gathered using a suitable thinking map.
4. Find the information on oxygen and carbon cycles and how they maintain the

percentage of gases in the atmosphere.
5. Present it in class.

Ways to Prevent Interferences in the Oxygen and Carbon Cycles

Our environment is being destroyed by human activities such as logging and the
uncontrolled usage of pesticides in agriculture. This will increase the amount of carbon
dioxide which interferes with natural cycles including the oxygen and carbon cycles.
Global warming and the greenhouse effect are among the consequences of
this interference.

Photograph 7.3 Fertile lands can become dry because of global warming
202 Chapter 7

Prohibit illegal log PCUehdnagpreatneral7a:nAkierpada Penyiasatan Saintifik
Photograph 7.4 shows some ways to reduce the problem of interferences to the
oxygen and carbon cycles on Earth.

Avoid using excessive pesticides
ging

s Prevent excessive release of smoke from vehicles
Photograph 7.4 Ways to reduce problems of interferences to the oxygen and carbon cycle

7.1
1. List the composition of air.
2. How can you identify oxygen and carbon dioxide?
3. What is the importance of carbon dioxide to plants?
4. What are the effects of the increase of carbon dioxide in the air to humans?
5. As a student who appreciates the importance of the carbon and oxygen cycles, suggest ways

to ensure a balance of carbon dioxide and oxygen content in the air.
Chapter 7 203
Reforestation
Do not burn forest

7.2 Combustion

Let’s learn

• Conclude about the conditions needed for combustion.
• Relate the conditions of combustion with the principles used in the manufacture of fire extinguishers.
• Practise safety measures to prevent the occurrence of fire which can lead to the destruction of life
and property.

C ombustion is the reaction that occurs when a substance is

heated in the presence of oxygen which produces heat
energy and light energy.
Oxygen
Fuel

Heat

Figure 7.8 Three conditions needed

for combustion

We can prevent
combustion if we
remove one of the B
conditions needed for Why do we use water to
extinguish fire?
combustion.

Photograph 7.5 The candle flame is
extinguished when oxygen is removed
by blowing it

Photograph 7.6 How can firefighters put out this fire?

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Carry out Activity 7.3 to prove that fuel, oxygen and heat are needed for combustion.

7.3

Aim: To prove that fuel, oxygen and heat are needed for combustion
I Fuel is needed for combustion

Materials and apparatus: Bunsen burner, tongs, lighter, glass rod, wood, candle, stone
Instruction
1. Light a Bunsen burner.
2. Hold a glass rod over the fire by using tongs.
3. Observe whether or not the glass rod burns.
4. Record your observation in a table.
5. Repeat steps 2 to 4 by using wood, candle and stone.

Material Observation
(a) Glass rod
(b) Wood
(c) Candle
(d) Stone

Questions
1. Based on your observation, classify the materials into fuel and non-fuel.
2. What is the conclusion that you can make from this activity?

II Oxygen is needed for combustion
Materials and apparatus: Gas jar, two white tiles, two candles of the same size,
plasticine, lighter

Instruction Gas jar
1. Hold two candles of the same size on white

tiles by using plasticine (Figure 7.9).
2. Light candles X and Y.
3. Turn a gas jar over candle X.
4. Observe which candle extinguishes first.

Plasticine

White White
tile
Questions tile Candle X Candle Y
1. Which candle burns longer? Why?
2. What is the gas used during the burning Figure 7.9

of candle?
3. What is the conclusion that you can make from this activity?

Chapter 7 205

III Heat is needed for combustion
Materials and apparatus: Match stick, match stick which has been stored inside the
refrigerator, matchbox
Instruction
1. Label the match stick which has been stored inside the refrigerator as P and the other

match stick as Q.
2. Light match sticks P and Q. Observe the changes that occur.
Question:
1. Do both match sticks ignite? Why?
2. What is the conclusion that you can make from this activity?

Fire Extinguisher

Have you gone through a fire drill at your school? The
firefighters would have shown the correct way to use the fire
extinguisher. The fire extinguisher is a protective tool that is
used to put out a fire or handle a small fire, usually during an
emergency. The substance used in a fire extinguisher differs based
on the type of materials on fire as shown in Table 7.1.

Figure 7.10 A fire extinguisher

Table 7.1 Types of fire extinguisher for different sources of fire

Material on fire Example of material Type of fire extinguisher
Solid Wood, cloth, paper Water, dry powder
Liquid Oil, varnish, paint Foam, dry powder, carbon dioxide
Gas Propane, acetylene, methane Foam, dry powder, carbon dioxide
Metal Potassium, sodium, magnesium, Dry powder, dry sand
calcium

Science in Life No! Water is denser than oil and
it will sink below the oil. The fire
Kamal, hurry up!
Pour a pail of will not be extinguished. We
must use foam!
water before the
fire spreads!

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PCUehdnagpreatneral7a:nAkierpada Penyiasatan Saintifik

As you have learned in subtopic 7.1, combustion needs oxygen, heat and fuel.
Therefore, fire can be extinguished by removing one of the conditions needed for
combustion using the following techniques.
(a) Covering: cutting off the contact of the fuel with
Science Exploration

oxygen or air. For example, covering the surface of fuel Fire blanket is a special
with fire blanket, wet sack, mud, sand, soil or foam. blanket made of fire
(b) Cooling: cooling the surface of burning materials by resistant substances. This
blanket covers the fire
spraying water or a layer of carbon dioxide. and prevents oxygen from
(c) Reducing the amount of burning materials/cutting seeping below the blanket
which will eventually
off the source of fuel: this technique can be used extinguish the fire.
by separating the burning materials, keeping away
materials that have not burnt yet and cutting off the

supply of gas or oil.

Photograph 7.7
A fire blanket

Safety Measures to Prevent the Occurrence of Fire

Keep away
flammable
substances
from fire

Keep matches and Safety Always be aware of your
lighters in a safe place measures to electrical appliances
prevent the
occurrence of

fire

Do not throw away Install fire alarm and smoke Do not plug in too many
cigarette butts when detector at home electrical appliances to a
they are still burning single electrical source

Figure 7.11 Safety measures to prevent the occurrence of fire

Chapter 7 207

7.2
1. Define combustion.
2. What are the conditions needed for combustion?
3. Luqman uses a fire blanket to put out a small fire at his house. How does the fire

blanket work?
4. Give four ways to prevent fire.
5. Metals like potassium and sodium are kept in paraffin oil. Why?

7.4 21 ISS

Aim: To make a poster on causes of fire and ways to prevent it
Instruction
1. Prepare a poster entitled ‘Causes of Fire and Ways to Prevent it’ in a group.
2. Present the best three posters on the science board of your class.

7.3 Air Pollution

Let’s learn

• Define air pollution and air pollutants.
• Communicate about air pollutants and the causes.
• Justify steps to prevent and control air pollution.
• Solve problems on the adverse effects of air pollution.

Air pollution is a situation which involves the presence of any pollutants in the air.

This brings harm and discomfort to living things and destroys the environment.
Air pollutants come from various sources. The sources of air pollutants are shown
in Figure 7.12.

Photograph 7.8 Air pollution from a
factory

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Pollutants Sources Sources
Smoke, soot, dust, • Exhaust of vehicles • Open burning
carbon monoxide, • Factories • Cigarettes
sulphur dioxide, nitrogen • Forest fires
dioxide, plumbum Pollutants
Dust, soot, Sources
smoke • Construction sites
• Asbestos factories
• Limestone quarries

Pollutants Sources Pollutants
Radioactive Nuclear Aerosol spray,
power plants chemical
materials fertilisers
Sources
Agriculture and Pollutants
plantation activities • Dust, soot

Sources Pollutants
• Air-conditioners Chlorofluorocarbon (CFC)
• Refrigerators
• Aerosol sprays
• Electronic factories

Figure 7.12 Sources of air pollutants

7.5

Aim: To discuss air pollution problems
in Malaysia
Instruction
Photograph 7.9 shows the hazy condition in Kuala
Lumpur in 2015. Discuss in groups the definition
of air pollution and sources of air pollutants
which cause haze. Then, present your discussion
in class.

Photograph 7.9 Haze in Kuala Lumpur

Polluted air can cause illness and discomfort to humans. There are various steps
that can be taken to prevent and control air pollution. Figures 7.13(a) and (b) show the
effects of air pollution and ways to prevent and control it.

Chapter 7 209

Health

• Smoke and dust can cause breathing problems
• Sulphur dioxide can cause respiratory problems
• Carbon monoxide can cause headache, mental

retardation and death
• Asbestos particles can cause lung cancer
• Lead particles can cause intellectual disability among

children and babies

Buildings and infrastructures

• Dust and soot stain buildings
• Acid rain corrodes concrete

and limestone buildings
• Acid rain speeds up iron

rusting

Causes and effects
of air pollution

Plants and animals

• Acid rain makes the soil acidic and less fertile
• Acid rain makes the source of water acidic and

not suitable for aquatic life
• Smoke and haze decrease the amount of sunlight

reaching the Earth and decrease the rate
of photosynthesis.

Climate
• Smoke from factories, vehicles and open burning lead to haze
• Excessive carbon dioxide contributes to greenhouse effect
• Excessive chlorofluorocarbons (CFC) causes the thinning of the

ozone layer
• Sulphur dioxide and nitrogen dioxide cause acid rain

Figure 7.13 (a) Causes and effects of air pollution

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Law Enforcement

• Fine smokers who smoke at restricted areas
• Fine individuals who conduct open

burning
• Fine drivers whose vehicles emit excessive

smoke
• Prohibit factories from being built at

housing areas

Ways to prevent and Education
control air pollution
• Educate students about the effects of
air pollution and ways to prevent it

• Organise anti-smoking campaigns
• Encourage the public to walk or

ride bicycles
• Encourage the usage of public

transport or car pooling

Science and Technology
• Implement hybrid technology in vehicles
• Choose refrigerators which use hydrochlorofluorocarbons

(HCFC) instead of chlorofluorocarbons (CFC)
• Install filters in smoke chimneys at factories
• Use catalytic converters on vehicles
• Replace the use of pesticide with biological control to

control pest

Figure 7.13 (b) Ways to prevent and control air pollution

Chapter 7 211

7.6

Aim: To gather information on effects of air pollution on living things and the
environment, and the steps taken by authorities in controlling air pollution.
Instruction
1. Work in groups.
2. Each group has to choose an area in Malaysia which has a high rate of air pollution.
3. Gather the information below from your chosen area:
(a) the effects of air pollution towards the health of the community, animals, plants,

buildings and infrastructures.
(b) efforts taken by the authority, for instance Jabatan Alam Sekitar, to overcome the air

pollution problem.
4. Present your findings in class.

7.3
1. What are the pollutants that can cause haze?
2. As a student, how can you increase the awareness of air pollution in the community?
3. Give three reasons why it is important to keep the air clean.
4. Littering can also cause air pollution. Explain how littering causes air pollution.
5. Match each pollutant to its effect.

Pollutant Effect
Carbon dioxide Acid rain
Nitrogen dioxide Greenhouse effect
Chlorofluorocarbons Thinning of the ozone layer

6. Tick (✓) the correct statement on how to control and reduce air pollution.
(a) Use materials free of chlorofluorocarbons (CFC).
(b) Use public transport.
(c) Conduct open burning.
(d) Practise reusing and recycling items.
(e) Use petrol and diesel that contain lead.

212 Chapter 7

Air

Composition of air Carbon cycle and Combustion Air pollution
oxygen cycle Definition
Gas Other Carbon cycle Conditions of Fire Air pollutants and
components maintains the combustion extinguisher causes
Nitrogen content of Effects of air
Oxygen Water vapour carbon dioxide Oxygen Foam pollution
Carbon Dust in the air Heat Water Ways to prevent and
dioxide Microorganisms Oxygen cycle Fuel Dry powder control air pollution
maintains the Carbon
content of dioxide
oxygen in the air Dry sand
PCUehdnagpreatneral7a:nAkierpada Penyiasatan SaintifikInert gases
Chapter 7 213

After learning this chapter, you are able to:
7.1 Composition of Air

Plan ways to determine and record the composition of air
Synthesise the composition of air from a pie chart
Justify the importance of oxygen, nitrogen, carbon dioxide and inert gases in daily life
Appreciate the carbon cycle and the oxygen cycle in maintaining the composition of gases in the air
Solve problems when there is/are interference to the oxygen and carbon cycles
7.2 Combustion
Conclude about the conditions needed for combustion
Relate the conditions of combustion with the principles used in the manufacture of fire extinguishers
Practice safety measures to prevent the occurrence of fire which can lead to the destruction of life
and property
7.3 Air Pollution
Define air pollution and air pollutants
Communicate about air pollutants and the causes
Justify steps to prevent and control air pollution
Solve problems on the adverse effects of air pollution

Summative Practice 7

1. The pie chart in Figure 1 shows the percentage of gas P, Q, R and S in the atmosphere.

Q = 21%

R = 0.97% P = 78%
S = 0.03%

Figure 1

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(a) Determine gas
(i) P (iii) R
(ii) Q (iv) S
(b) State the importance of gas P.
(c) What would happen to the temperature of Earth if the percentage of gas S increases?
Give a reason for your answer.
(d) Give one reason why air is considered a mixture.

2. Solve the crossword puzzle below with the correct answer.



(c)

T (d)

(a) D

BO (b)

GN

N

E

Horizontal:
(a) Carbon cycle maintains this gas in the air.
(b) This gas is used to fill up light bulbs.
Vertical:
(c) A layer that surrounds the Earth.
(d) This gas is needed in combustion.

Chapter 7 215

3. Figure 2 shows the percentage of carbon dioxide in a period of time.

Carbon dioxide in atmosphere (%) 1995 2000 Year
2005
0.036
0.035
0.034
0.033
0.032
0.031
0.030
0.029
0.028
0.027

1875 1880 1885 1990

Figure 2
(a) Logging activities increase the amount of carbon dioxide in the atmosphere. How does it

contribute to the increase of carbon dioxide level in the atmosphere? Explain.
(b) Other than logging, give one activity that contributes to the increase of carbon dioxide in

the atmosphere.
(c) State two effects if the rate of carbon dioxide in the atmosphere increases continuously.

4. Ammar witnessed a fire at a workshop on his way home from school. The fire was caused by a
short circuit.

(a) What is combustion?
(b) State the conditions of combustion.
(c) Based on the situation,
(i) how does one prevent such a fire from happening?
(ii) what fire extinguisher is suitable?
(d) State three precautions that should be practised to prevent fire from happening.



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PCUehdnagpreatneral7a:nAkierpada Penyiasatan Saintifik
5. Figure 3 shows a situation that occurs in Kuala Lumpur.

Figure 3
(a) What is the environmental problem shown in Figure 3?
(b) State two effects of the problem you mentioned in 5(a) towards health.
(c) The road accident rate increases when this environmental problem occurs. Why?
6. The oxygen level in a cave would eventually decrease as we walk further into the cave.


Figure 4
(a) List a few reasons why the oxygen level decreases in the cave.
(b) If we want to go into a deep cave, we are encouraged to bring torches with us in addition

to torchlights as an indicator to show the presence of oxygen. How does the torch
function? Explain.
(c) Do you think it is good to bring torches into the cave?
(d) Suggest one way to detect the oxygen level in a safer way. Give one reason for
your suggestion.

Chapter 7 217

7. A company wants to do a limestone quarry project near Kampung Permai. The village headman
has conducted a meeting with the villagers. The result from the meeting is as follows:

Table 1 20
Percentage of villagers supporting the quarry project (%) 80
Percentage of villagers opposing the quarry project (%)

(a) Why do you think a majority of the Kampung Permai villagers oppose the quarry project?
Give a cause for their concern.

(b) Villagers who support the quarry project have a common reason, which gives them one
advantage. What is the advantage?

(c) The village headman has decided to go against the quarry project.
Is it a rational decision?

8. Assume that you are a scientist. The amount of sunlight received in East Asia has decreased due
to dust produced from natural disasters such as volcano eruptions and development activities.
Consequently, many plants planted by farmers die. How does this happen? Suggest ways how
the farmers can solve this problem.

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4 Energy and of Life
Sustainability

Light is a form of energy that helps
us see scenery and objects around
us. Without light, the world will be
dark and our life will become dull. We
should be grateful for the presence of

light in our life.

ChapBtaebr 8 219

8Chapter Light and Optics

Why do the sky and the sea look
blue when the sun is shining?

Why does the seabed look shallow?
How is the shadow of a coconut
tree formed?
What causes these phenomena
to occur?

Let’s study: Dispersion of Light
Scattering of Light
The Use of Mirrors Addition and Subtraction
Characteristics of Light of Light
Reflection of Light
Refraction of Light

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SCIENCE BULLETIN

PHENOMENON OF RAINBOW FORMATION

O btpuchyhsoeeemSdfnii pourrwasomrItipnstupeahrenniaensdacrotmsenscNoreostnoreotlifawowesntusthehdorpoeosinnaf.fmrgioeanxraotmeptnfheaawlergitigihyemohidentteeatnaroolntfi1sgud6rhcna7cotdi2onnie.lnbdroHtsouuotwcaeristn.tewsdNbdaeteshgweatnon

Angle of reflection Refraction
Real Dispersion
Virtual Object distance
Reflection Image distance

ChapBtaebr 8 221

8.1 The Use of Mirrors

Let’s learn

• Differentiate between a real image and a virtual image.
• Communicate about the characteristics of image formed by a plane mirror, concave mirror and

convex mirror.
• State that the object distance is equal to the image distance in a plane mirror.
• Use the plane mirror to apply the concept of reflection of light.
• Justify the application of concave mirrors and convex mirrors in daily life.
• Construct an optical instrument to appreciate the use of these optical instruments to enhance the ability

of the human senses.
• Solve problems in daily life involving the application of plane mirrors, concave mirrors and convex mirrors.

We see our image in the mirror every day. Do you know what
type of mirror we use?

This type of mirror is a plane mirror. What image is
formed in the plane mirror? Real image or virtual image?

8.1 Photograph 8.1 An image seen in a mirror

Aim: To study the difference between real image and virtual image

Materials and apparatus: A piece of black A4 cardboard, a piece of white A4 cardboard, a
candle, pin, mirror.

Instruction Black Image of
1. Use a pin to pierce a hole in a cardboard candle
black A4 cardboard. White
2. Arrange the materials and apparatus as Candle cardboard
Pinhole as screen
in Figure 8.1. Use a white A4 cardboard
as a screen where the image will be Figure 8.1
formed.
3. Observe the image formed on the Mirror
second cardboard which is used as a Image
screen.
4. Choose a student to stand in front
of a mirror as shown in Figure 8.2.
Observe the image formed.

Questions Figure 8.2

1. Is the image formed in Figure 8.1 real or virtual?
2. Compare the characteristics of the image formed in Figure 8.1 with Figure 8.2.

A real image is an image that forms on a screen, while a virtual image is an image
that cannot be formed on a screen. Our image forms behind the mirror, not on the
mirror screen. Therefore, the image formed by a plane mirror is a virtual image.

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What are the characteristics of the image
formed by a plane mirror, a concave mirror and
a convex mirror (Figure 8.3)?

PlanePmPirror P CoQncQave mQirror RCoRnvexRmirror
Figure 8.3 Types of mirrors

8.2

Aim: To determine the characteristics of the image formed by a plane mirror, concave
mirror and convex mirror

Materials and apparatus: Plane mirror, concave mirror, convex mirror, candle, graph paper.

Instruction
1. Place a candle on a piece of graph paper in front
of a plane mirror as shown in Figure 8.4. Plane Location
mirror of image
2. Observe the image formed. Is the image the
same size, smaller or bigger than the object? Candle Graph
3. Repeat steps 1 and 2 by replacing the plane mirror paper
with a concave mirror and a convex mirror.
4. Record the results in a table.
Figure 8.4

Type of mirror Image formed (same size / smaller / bigger) than object
Plane mirror
Concave mirror
Convex mirror

5. Then, measure the distance of the image from the plane mirror.
Distance of image from the plane mirror = squares on graph paper.

Questions
1. Compare the size of the image formed in the mirrors with the size of the object.
2. Compare the distance of the image formed in the plane mirror with the distance
of the object.

A plane mirror applies the concept of light reflection Light rays
as in Figure 8.5. Light rays that shine on the mirror
will be reflected. Surface of mirror
Figure 8.5 Reflection of light

ChapBtaebr 8 223

Usage of Plane Mirror, Concave Mirror and Convex Mirror

Do you know that the plane mirror, concave mirror and convex mirror are widely used?

Plane A plane mirror makes a living
mirror room look spacious.

A plane mirror helps a dancer to
correct his movement.

Photograph 8.2(a) Usage of plane mirrors

A concave mirror helps to Concave A concave mirror is used by a dentist to see
magnify the image to make mirror the patient's teeth so that the image formed
it easier for someone to looks bigger and closer.
apply make up.

Photograph 8.2(b) Usage of concave mirrors

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A convex mirror is used as a safety feature at Convex Convex mirrors at the supermarket can
dangerous corner of a road. mirror help a shopkeeper to see every corner
of the supermarket to prevent theft.

Photograph 8.2(c) Usage of convex mirrors

Convex mirrors and concave
mirrors
http://www.animations.
physics.unsw.edu.au/jw/light/
mirrors-and-images.htm

8.3 21 ICS

Aim: To discuss the usage of plane mirrors, concave mirrors and convex mirrors
Instruction
1. Work in groups.
2. Discuss the usage of plane mirrors, concave mirrors and convex mirrors.
3. Present your discussion using multimedia presentation.

ChapBtaebr 8 225

Optical Instruments that Apply the Concept of Reflection

of Light Periscope

Optical instruments are invented by scientists based on the
concept of light reflection to enhance the ability of human
senses. We should be grateful for these inventions and
appreciate them.

Submarine

Periscope 45° Mirror
Periscope is an instrument used in submarines to observe
the sea surface. Periscope works by using the concept of 45°
reflection of light. Light from the sea surface is hit through the
top mirror and is reflected. The light is then reflected again
at the second mirror, right into the eye of the observer in the
submarine. Let us create a simple periscope in Activity 8.4.

Mirror

8.4 Figure 8.6 A periscope

Aim: To create a simple periscope Box

Materials and apparatus: Two plane mirrors, 15 cm

box, knife. 14 cm

30 cm

Instruction Two pieces of
plane mirror
1 2 10 cm 15 cm

Cut Mirrors facing
with a each other
knife

Cut the side of the upper Place the mirrors facing
and lower box to fit the each other.
width of the mirror.

3 4 Mirror Be careful when using
knives to prevent injuries.
Hole 1 Object

Hole 2 See the objects
through the Hole 2.

Make two holes exactly Place the object to be
opposite each mirror. viewed in front of Hole 1.

Figure 8.7 Steps to create a periscope

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Kaleidoscope

Kaleidoscope is a toy made using plane mirrors. With this toy, you can create various
amazing patterns. These patterns are obtained due to the repeated reflection of the image
of the objects inside the kaleidoscope. Therefore, the number of images seen is more than
the number of objects. Let's carry out Activity 8.5 to build a kaleidoscope.

8.5

Aim: To build a kaleidoscope Mirror 2 pieces of
card plastic discs

Materials and apparatus: One kitchen A

towel roll, three pieces of mirror cards, Scissors
colourful beads, two pieces of plastic
discs, scissors, glue, cellophane tape,
colourful paper for decoration, round
black cardboard. Glue

Instruction Colourful B Cellophane
tape
1. Prepare the materials and beads Kitchen Round black
towel roll cardboard
apparatus as shown in Figure 8.8.
2. Prepare three pieces of mirror cards. Each one is
4.3 cm in width and 21 cm in length. Figure 8.8

3. Stick the three pieces of the mirror cards with
cellophane tape to make a triangle prism. Make sure
the shiny surface is facing inward.
4. Push the triangle prism into the empty roll (Figure 8.9(a)).
5. Cut two pieces of round plastic discs with a diameter of 5.3 cm respectively.
6. Attach the first plastic disc on one end of the roll, A (Figure 8.9(b)). Push the first plastic
disc into the roll until it touches the triangle prism.

A A

Triangle Empty kitchen Plastic
prism B towel roll disc

(a) (b) B
Figure 8.9

7. Add colourful beads on the surface of the first plastic disc (Figure 8.10(a)). Attach the
second plastic disc to cover the colourful beads (Figure 8.10(b)).

A Plastic disc A

(a) B (b) B
Figure 8.10
ChapBtaebr 8 227

8. At the other end of the kitchen towel roll, B, attach a Round black
round black cardboard which has a diameter of 5.3 cm cardboard
and make a hole on it (Figure 8.11).
B
9. Decorate the kitchen towel roll with colourful
papers according to your creativity. A

10. Look at the pattern of the colourful beads formed
through the hole.

Figure 8.11

Science in Life 21 CPS

Situation 1

How do I see the scenery Well, a periscope can
behind this wall? help me.

Situation 2 We can fix convex mirrors at
It is dangerous to dangerous corners.
walk on this path
because we cannot Convex
mirror
see anything around You can fix a
the corner. convex mirror on
the bike to see
Situation 3 things behind you.
It is good if I can see
things behind me to Convex mirror
avoid accidents.

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8.1
1. The picture shows a man standing in front of a mirror. What type of

mirror is it? State the characteristic of the image formed.
2. What is the function of plane mirrors in a periscope?
3. Why do we need plane mirrors in a lift?

8.2 Properties of Light

Let’s learn

• Communicate about the properties of light.

W hat are the properties of light? Why do we see

lightning before we hear thunder?

The speed of light is 3.0 × 108 m s–1. Photograph 8.3 A lightning
Light travels much faster than
sound, so we see the lightning
before we hear the thunder.

Albert Einstein

Light travels in straight lines. We can see the
movement of light in a light show (Photograph 8.4).
Have you ever wondered how shadows
are formed?

1. Sunlight travels Photograph 8.4 A light show
in straight lines. 2. Umbrella is an opaque
object, therefore the
sunlight cannot pass
through it.

Photograph 8.5 Formation of shadows 3. When light is blocked
by an opaque object, a
shadow is formed behind
the opaque object.
ChapBtaebr 8 229

Do you know that your shadow will become short in
the afternoon and long in the evening?
Another property of light is that it can be dispersed
by water droplets in the sky to form a rainbow as in
Photograph 8.6.

Photograph 8.6 A rainbow Photograph 8.7 The Sundial
The Sundial was used in ancient
Science Exploration times to determine the time
Did you know that shadow puppets use the during the day. The sundial used
concept that shadows are formed when light the concept that shadows are
is blocked? formed when the sunlight is
blocked by objects.

Photograph 8.8 Shadow puppets

8.2

1. Hisyam’s shadow is the shortest in the when the Sun is his head.
2. The diagram shows two opaque objects blocking the light
from a torchlight. Screen

Draw the shape of the shadow that will be formed on the screen.

Wooden
blocks

8.3 Reflection of Light

Let’s learn

• State the characteristics of the image formed by a plane mirror.
• Communicate about the Law of Reflection.
• Draw ray diagrams to show the reflection of light
• Solve problems in daily life with the application of reflection of light.

Y ou have learned how an image is formed in a plane mirror using the concept

of reflection. Do you still remember the characteristics of the image? What are the
other characteristics of the image formed by a plane mirror?

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Table 8.1 shows the characteristics of the image formed by a plane mirror.

Table 8.1 Characteristics of the image formed by a plane mirror

(a) Upright (b) Object size, H = Image size, h
(c) O bject dOi Astance, = image dOiBstance,
The image formed by a
Boy Image plane mirror is:
• upright
Hh • laterally inverted
• same size as the object
OA OB • virtual
• of the same distance as

the object distance

(d) Laterally inverted (e) Virtual

Object Image Virtual
image
B B
Object

OA OB

Law of Reflection

When a beam of light is directed onto a piece of a plane mirror at a certain angle (angle
of incidence, i), the light ray will be reflected to a certain angle (angle of reflection, r).
What is the relationship between the angle of incidence and angle of reflection? Carry out
Experiment 8.1.

Experiment 8.1

Problem statement: What is the relationship between the angle of incidence, i and angle
of reflection, r?

Hypothesis: The angle of incidence, i is the same as the angle of reflection, r.

Aim: To determine the relationship between the angle of incidence, i and angle of
reflection, r
Plane mirror
Variables White paper

Manipulated variable: Angle of incidence, i Slit i r
Responding variable: Angle of reflection, r
Constant variable: The size of slit
Normal line
Materials and Apparatus: Plane mirror, ray box,
power supply, white paper, protractor.
Ray box

Procedure Figure 8.12
1. Carry out this activity in the dark.
2. Arrange a ray box and a plane mirror on a sheet of white paper.
3. Direct the light beam towards the plane mirror at an angle i = 10°.
4. Measure the angle of reflection, r.
5. Repeat steps 3 and 4 with angle of incidence, i = 20°, 30°, 40° and 50°.

ChapBtaebr 8 231

6. Record your results in a table.
Results

Angle of incidence, i (°) Angle of reflection, r (°)
10
20

Conclusion
Is the hypothesis accepted?
What is the relationship between the angle of incidence, i and angle of reflection, r?

Light reflected obeys the Law of Reflection:

a. The incident ray, the reflected ray, and the normal line all lie on the same plane.
b. The angle of incidence, i is equal to the angle of reflection, r.

Normal line

Incident ray Reflected ray The angle of incidence,
i is equal to the angle of
ir
reflection, r.
Plane mirror i=r
Figure 8.13 Reflection of light
Science Exploration
Applications of Reflection of Light

Photograph 8.10 Applications of reflection of light Photograph 8.9
An ambulance
8.3 Have you ever wondered
why the word “ambulance”
is written in an inverted
manner? How is the image
formed when the drivers
of other vehicles look into
their rear view mirror?
Think about it.

1. Explain the Law of Reflection with the help of a light reflection ray diagram.
2. Complete the statement below.
The image formed by a plane mirror is , , and the
image distance is with the object distance.

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8.4 Refraction of Light

Let’s learn

• Generalise that refraction occurs when light moves through medium of different densities.
• Draw ray diagrams to show refraction of light when light propagate from one medium to another

medium of a different density.
• Generalise the relationship between the angle of incidence, i and angle of refraction, r, when light

travels from a medium of low density to a medium of high density.
• Justify the applications of refraction of light in daily life.

Why does a deep pond appear to
be shallower and the fish in the
pond appears to be much closer to

the water surface?

Photograph 8.11 Fish in the pond
Why does a pencil
look bent in a glass

of water?

Photograph 8.12 A pencil looks bent

The illusions above occur as a result of the change in the direction of movement of
light when light travels through two mediums of different densities. This phenomenon is
known as refraction of light. Can you give examples of other refraction of light?

ChapBtaebr 8 233

Observer

Light

Image
seen

Fish appears to be much
shallower than its real

location due to the
refraction of light.

Actual location 21 CPS
of fish
B
Figure 8.14 Fish in an aquarium Due to the refraction of
light phenomenon, how
do you catch fish in a
river?

Figure 8.15 shows the refraction of light when light rays pass through mediums of
different densities.

Normal Normal

Incident ray Incident ray

Water Air
(more dense) (less dense)
Water (more dense)
Air
(less dense) Refracted
ray
Refracted
ray The light ray is refracted towards the normal
when the incident ray moves from a less
The light ray is refracted away from the dense medium to a more dense medium.
normal when the incident ray moves from
a more dense medium to a less dense Normal
medium.

Normal

Incident Water Incident Air
ray (more dense) ray (less dense)

Refracted Air Refracted Water
ray (less dense) ray (more dense)

The light ray is not refracted when The light ray is not refracted when
the incident ray is parallel to the the incident ray is parallel to the
normal and moves from a more normal and moves from a less
dense medium to a less dense dense medium to a more dense
medium. medium.

Figure 8.15 Ray diagrams to show refraction of light

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Experiment 8.2

Problem statement
What is the relationship between the angle of incidence, i and angle of refraction, r when
light travels from a less dense medium to a more dense medium?
Hypothesis: The greater the angle of incidence, i, the bigger the angle of refraction, r.
Aim: To determine the relationship between angle of incidence, i and angle of refraction, r
when light travels from a less dense medium (air) to a more dense medium (glass block)

Variables
Manipulated variable: The angle of incidence, i
Responding variable: The angle of refraction, r
Constant variable: The size of the slit, the shape of glass block
Materials and apparatus: Glass block, ray box with single slit plate, plastic ruler, power
supply, white paper, protractor.

Procedure White paper
1. Carry out this experiment in the dark.
2. Place a glass block on a white paper and trace its r Glass
block
outline.
3. Direct a single incident ray onto the block, mark its i Slit

path and draw its incident ray with a ruler. Ray box
4. Mark the path of the ray emerging from the block and Figure 8.16

draw the ray with a ruler.
5. Remove te block, connect the entry and exit points to

show the path of the ray inside the block.
6. Draw a normal line at the entry point.
7. Measure the angle of incidence, i and the angle of

refraction, r using a protractor.
8. Repeat steps 3 to 7 for different angles of incidence.
9. Record your results in a table.

Results

Angle of incidence, i (°) Angle of refraction, r (°)

Discussion
1. Plot a graph of i against r.
2. Based on the graph of the angle of incidence, i against the angle of refraction, r, what is
the relationship between the angle i with the angle r?
Conclusion
Can the hypothesis be accepted?

ChapBtaebr 8 235

Question
What happen to the light ray when it travels from a
(a) less dense medium to a more dense medium?
(b) more dense medium to a less dense medium?
We can see many examples of the effects of light refraction in our daily life. Let us
carry out Activity 8.6 to discover even more light refraction phenomena.

8.6

Aim: To investigate the phenomenon of refraction of light
Instruction
1. Work in groups.
2. Use resources such as the library, Internet, and others to collect information

regarding the following phenomena.
• A spoon looks bent in water
• The bottom of a pool appears to be shallower
3. Present the outcomes of your research in class.

8.4
1. Why does the bottom of a deep swimming pool appear shallower?
2. Light rays refract at a certain angle in two different cases as below. Differentiate the density

of the two mediums for both the cases below.

Case 1: Case 2:
A C
B D



8.5 Dispersion of Light

Let’s learn

• Communicate about the dispersion of light.
• Explain the dispersion of light in daily life with examples.

D o you know why the components of colour in a rainbow can be seen when light

passes through a glass prism (Figure 8.17)?
White light consists of seven components of colour. Each component of colour travels
at a different speed in a medium. For example, red light has the highest speed, so red light
is refracted the least. However, violet light has the lowest speed, so violet light is refracted
the most.

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1 When a white light ray is directed to a prism, the white B
light will be separated into its components of colour.
This is because the different colours in the white light What will happen if a
bend towards the normal at different angles when second inverted prism is
entering the prism. placed behind the first
prism?

21 CPS

2 When the different colours leave
the glass prism, they are refracted
away from the normal. The
different colours are dispersed
in an order that is known as a
Normal S spectrum. The spectrum of white
P
White E
light C light consists of red, orange, yellow,
T green, blue, indigo and violet
R
U colour.
M
Glass prism

Figure 8.17 Dispersion of white light by a glass prism

When sunlight enters rain droplets in the
sky, the white light will be refracted and
dispersed into seven different colours to
form a rainbow.

Figure 8.18 The formation of rainbow

ChapBtaebr 8 237

8.7

Aim: To study the dispersion of light passing through a glass prism and the formation
of rainbow
Materials and Apparatus: Glass prism, white screen, ray box, a plane mirror, water,
torch light, a piece of white paper, a basin, cellophane tape, a round black cardboard.
Instruction

I Dispersion of light by a glass prism

White light

Ray box Glass prism
White screen

Figure 8.19
1. Carry out this activity in the dark.
2. Direct a narrow light ray from a ray box towards a glass prism (Figure 8.19). Adjust

the glass prism slowly until a sharp colour spectrum is formed on a white screen.
3. Identify the colours formed on the white screen.
4. Observe the order of colours on the white screen.
5. Record your observation.

II Formation of a Rainbow Torch
light

1. Fill a basin half-full with water. Black

2. Place a piece of mirror in the water with cardboard White
an incline on the side of the basin. Secure paper

the mirror using a cellophane tape.
3. Make a small hole on a piece of round black Cellophane

cardboard. Then, attach the cardboard tape

to the front of a torch light. Mirror

4. Shine the torch light towards the mirror (Figure 8.20). Figure 8.20
5. Hold a white paper beside the mirror. Adjust the direction of the torch light until you
see a rainbow on the paper.

8.5

1. List the seven colours formed on the screen below in the correct order.
2. State the colour component that is refracted the most White light
and refracted the least in the phenomenon above.
Relate the phenomenon with the speed of each
colour component. Ray box Glass prism
White screen

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8.6 Scattering of Light

Let’s learn

• Communicate about scattering of light.
• Explain scattering of light in daily life with examples.

W hy does the sky appear blue at midday and reddish in the evening?

Photograph 8.13 The phenomena of scattering of light
The two natural phenomena are caused by the scattering of light. Scattering of light
occurs when light is reflected in all directions by clouds or particles in the air.

During midday Blue light is scattered During midday, blue light
by particles in the air is scattered the most in all
Air particles directions by the tiny particles
and dust in the atmosphere. Therefore,
the sky looks blue during
midday.

Earth

Figure 8.21 Scattering of light during midday

ChapBtaebr 8 239